1. Field of the Invention
This invention relates to a device for wetting a flexible mat-shaped carrier material comprising guiding elements for the transport and guiding of the carrier material configured in such a way that it least one hollow space limited by the carrier material is constituted into which a spray device can be introduced for wetting the upper surface of the carrier material which is turned to the inner side of the hollow space. Furthermore, the invention relates to a method for wetting a flexible mat-shaped carrier material in which the carrier material is guided by constituting at least one hollow space and the upper surface of the carrier material which is turned to the inner side of the hollow space is wetted.
2. Description of Related Art
A device and a method of the above mentioned type are known, among others, from DE 196 33 656 C1. For the carrier materials, they can be, for example, nonwovens and fiber mats made of plastics, glass fibers and natural fibers, whereby these materials can exist as primary raw materials as well as as recycled materials or as a mixture thereof. Such carrier materials must often be provided with a stiffening matrix material by spraying on liquid existing components. For the liquid existing components, they are generally two-component resins, for example polyurethane resins, epoxy resins and the like. Due to the adhesive effect and the curing process, there result moulded parts with an inherent stability which can be used, for example, in the automotive industry, in the furniture industry and for consumer goods. For the device for wetting such mat-shaped carrier materials according to DE 196 33 656 C1, a continuous carrier material web is guided over deflection rollers as well as a chain conveyor guide through a wetting device in which it can be wetted on both faces. For this purpose, the carrier material web is guided over two parallel tunnel chain wheels so that it constitutes the surface area of a cylindrical hollow space (tunnel, drum) between these wheels. The inner side of this surface area is then sprayed with the wetting agent and thus wetted on one face. The losses and emissions of the wetting agents to the outside are limited by the fact that the wetting takes place in the inner part of a hollow space. For the double faced coating of the carrier material web, a second pair of tunnel chain wheels is placed in the wetting device by means of which a second cylindrical (tunnel-shaped) hollow space is constituted. Hereby, the inner side of the surface area of the hollow space is however constituted by the other face of the carrier material, i.e. the face which is not yet wetted. Thus, the second side of the carrier material can also be wetted in this second hollow space.
Moreover, methods are known for which two carrier material mats are simultaneously worked, since they constitute together a hollow space for wetting because of corresponding guides. Here, a double-faced coating can also be achieved by turning the two mats.
The so-called high-pressure spray technique constitutes a further state of the art. Wetting agent spray mist is produced here with high pressure and with a relatively high flow rate of additional air. High-pressure spray heads work with an admission pressure up to 80 bar and also use this high pressure for a hydrodynamic mixing effect in the spray head.
The spray heads are most of the time guided by a robot. The output of such systems reaches 2 to 3 m2/min (one-faced) depending on the precision requirements. Since this method is very flexible to use because of the free programmability and is variable with respect to the quantities to be sprayed, it requires high investment costs and a high regular expenditure of cleaning which reduces the daily availability of the system. Furthermore, the system requires much space for the equipment for a relatively low output per area unit. The high overspray quantities, i.e. the quantities of wetting agent which do not reach the aimed place and are sprayed lost in the environment, are also disadvantageous. Finally, there also result high waste quantities of production auxiliary materials, such as for example covering foils.
For the roller-laminating methods, wetted spreader rolls apply the wetting agent onto the carrier materials. Herbey, there does not result or there only results little overspray and only a slight pollution of the ambient air. Moreover, these methods achieve a high output per area unit but cause considerable pollution problems in the installation.
Furthermore, linearly guided spray heads in spray tunnels are known. These spray heads require slightly less investment costs and less installation surfaces than the high-pressure spray technique for the same output per area unit. They can also be compared to those with respect to their daily availability and the secondary waste quantities. The spray systems can work with or without air (xe2x80x9cairlessxe2x80x9d).
Concerning the airless methods, spray heads with a mechanical compulsory mixer have been developed which can be operated with relatively low media admission pressure up to 15 bar and only very low quantities of additional air (Tartler company, Lxc3xc tzelbach, Germany). In a certain embodiment, as with a centrifugal wheel is provided with a continuous rotary axle which is preferably screw-shaped for the transport of the wetting agent to its front end. At the front end of the axle, there is a centrifugal :disk with a diameter of a few centimeters. The screw and the centrifugal disk rotate at work with numbers of revolutions up to 4000 revs./min. Due to the impact of the wetting agent onto the centrifugal disk, the wetting agent is centrifuged because of the centrifugal forces radially outwards where it reaches the object to be wetted. For wetting carrier materials in the mat cut-out piece with such a device, the mat can be fixed on the inner wall of a rotary drum. The mat upper surface turned to the inner side of the drum can then be wetted by the above described centrifugal wheel spray head. With this method, only one-faced wetting of the carrier materials is possible, since the inner side of the drum would be contaminated by the already wetted upper surface of the carrier material if the mat would be used turned in the drum. Since the wetting agents often are resin components and thus substances which can also be used as adhesives, the contamination of wetting installations with the wetting agent constitutes a particular problem.
It is a disadvantage of the above mentioned xe2x80x9cdrum wetting methodsxe2x80x9d, among others, that, when the installation is being switched off, they leave either only partially wetted raw mats (i.e. wetted on one face), or they require a relatively high expenditure of technique in order to avoid this. For example devices for the xe2x80x9cself threadingxe2x80x9d of the mat ends must be provided for. If two mat webs have to be worked simultaneously, due to the double layout of machine parts (unwinding, drying, material storing, discharging device, assembling device), this causes relatively high investment costs which can only be defended for an utilization of the very high possible output.
Furthermore, a non-homogeneity of the wetting result appears with the known drum wetting methods, when a horizontally guided centrifugal spray device is introduced into the hollow space (drum, tunnel).
Finally, with the methods with a chain or toothed disk guiding, the fault is found that they have practically no flexibility with respect to the variation of the cut-out dimension of the raw mat, which is however often desired for an optimization of the production.
The aim of this invention was to improve a device of the type mentioned above in such a way that its construction is simpler and that it can thus be produced with less costs, that the coating result is homogeneous and that cut-out dimensions as different as possible can be flexibly worked.
This aim is achieved in that the transport and guiding elements are constituted by a frame with side ledges into which a carrier material mat can be clamped, whereby at least one flexible side ledge can be reversibly brought from the stretched form into a bent form.
Accordingly, it is the question of a device for which, similarly to the xe2x80x9cdrum wetting methodsxe2x80x9d, a flexible mat-shaped carrier material is formed over guiding elements in such a way that a hollow space is created which is limited by the carrier material, hollow space into which a spray device can be introduced for wetting the inner side of the hollow space. According to the invention, the transport and guiding elements are constituted by a frame with side ledges in which a carrier material mat can be clamped, whereby the frame has at least one flexible side ledge which can be brought from the stretched form into a bent form (curved, buckled form) and back.
The device according to the invention thus realizes the transport and the configuration of a hollow space from the carrier material mat according to another principle than that of the prior art. Not an (endless) web of carrier material mats is transported and, due to a corresponding web guiding, the intermediate configuration of hollow spaces is provided for, but a single carrier material mat is first firmly tentered into a frame. The frame constituted by side ledges limits a surface, the size of which corresponds to the size of the mat, or the size of which is preferably somewhat bigger than the mat surface. A mat to be coated can then be gripped in the frame surface by means of appropriate retaining means such as, for example, clamps or hooks which are fixed to the side ledges of the frame. A mat which is placed in the frame in this way can be moved together with the frame at will and can especially be transported from a mat distribution station to a coating station and from there to a further processing station, for example to a press. The peculiarity of the frame consists in the fact that at least one side ledge is flexible. This means that it can be brought from the stretched, straight form to a curved or buckled form and back. Hereby, the side ledge can be continuously bendable like a metal wire but can also consist of rigid segments which are articulated the one with the other so that a polygonal tension is created by bending the side ledge. Due to the bending of the flexible side ledge, it is possible to bring the frame which is flat at the beginning with an even frame surface into a threedimensional form which substantially corresponds to a bent cylinder wall (with a circular or polygonal base). Thus, due to the bending of the side ledge, a hollow space is constituted by the carrier material mat clamped in the frame, hollow space into which a spray device can be introduced in a known way for wetting the inner upper surface of the hollow space. Compared with the spraying of an even surface, the constituting of the hollow space has the advantage that coating means losses are minimized due to the fact that the carrier material runs allround as far as possible.
The carrier frame which is used according to the invention has a considerably simpler construction than devices known from the prior art. A corresponding coating device can thus be produced with less costs. Furthermore, the mat cut-out can be variably held in certain limits, since mats of different sizes can be held on the side parts of the frame by fixing clamps with a different length or, due to a movable construction of an articulated arm, the distance between the clamps on the lateral articulated arms can be varied. The device according to the invention thus allows mat size variations up to 10% in both cut-out directions without any problem. Different cut-outs can even be alternately transported within these limits, for example for the front doors and the back doors of a vehicle. Hereby, the machine technical variations for a change of the cut-out size are automatizable. A further advantage of the device according to the invention consists in the fact that this device can be made with a considerably compacter construction, i.e. it requires less space than known devices.
In a further development of the invention the flexible side ledge can be brought into a curved form towards both sides of the frame surface. This means that the flexible side ledge can also take the curvature which is mirror-inverted to the first curvature. In this way, the invention achieves that a mat which is placed into the frame can constitute two different hollow spaces for which respectively another upper surface of the mat constitutes the inner side. Due to a curvature of the flexible side ledge into the first curvature direction and then into the second curvature direction, the clamped carrier material mat can be coated on both faces the one after the other.
A double-faced coatability of the carrier material mat could principally also be obtained by two different groups of flexible side ledges, whereby the first group guarantees the constitution of a hollow space with a first upper surface of the mat as an inner side and the second group a curvature by constituting a second hollow space for which the second upper surface of the carrier material mat forms the inner side. However, it is simpler for the construction to work with only one group of flexible side ledges and to configure these side ledges bendable in two directions. Such an arrangement also has the advantage that the coating of both hollow spaces can be carried out by the same spray device without complicated manipulations.
The side ledge can consist of several (rigid) segments connected with each other by hinged articulations. Such an assembly is easy to construct and guarantees a high frame stability since the articulations and the hinges can be constituted with practically any stability without this being detrimental to an easy bendability of the side ledge. Furthermore, the setting angles of the hinges can be easily controlled so that the movement and confirmation of the frame can be automatized.
In a further development of the invention, the whole frame is movably arranged, whereby it is preferably swivellable between at least one position with a horizontally orientated frame surface and at least one position with a vertically orientated frame surface. Due to the movability of the whole frame, the mat can be moved from a reception location to a coating station and from there to a further processing unit, for example to a compacting station. Since mats made of the carrier materials to be coated are generally supplied in the horizontal position, it is advantageous to be able to bring the frame into a horizontally orientated position for receiving and for clamping a mat. Moreover, it is advantageous to be able to bring the frame afterwards into a vertical position in which, due to a corresponding curvature of the flexible side ledge, a substantially cylindrical hollow space with a vertical axis can be constituted. For in this case, the spray device can be introduced into the hollow space along the vertical axis. This orientation of the spray device has the advantage that the effect of gravitation onto the spray mist does not cause an inhomogeneous coating result on the mat. Relating to the direction of the gravitation, the orientation of the vertical hollow space is symmetrical. This means a further advantage compared with the prior art for which only horizontally orientated hollow spaces (tunnels) are known in which, because of the gravitation, the respectively lower tunnel half is provided with a stronger coating.
The change in shape of the flexible side ledge preferably takes place over a driving motor and a corresponding gear. A determined curvature can be adjusted by means thereof in a simple manner, and the whole coating process can thus be automatized.
Furthermore, the invention relates to a method for wetting a flexible mat-shaped carrier material for which the carrier material is transported by constituting at least one preferably cylindrical hollow space and the upper surface of the carrier material orientated to the inner side of the hollow space is wetted. This method is characterized in that a carrier material mat is tentered onto a carrier frame and the hollow space is formed by bending a flexible side of the carrier frame.
Such a method has the advantage that the mat to be coated can be fixedly clamped into a carrier frame and that no expensive means have to be provided for threading and for a stable guiding of the mat during the transport. The mat which is placed in the carrier frame can rather be manipulated in a simple way with the whole carrier frame or over the carrier frame. By bending a flexible side of the carrier frame, the mat to be coated can be so formed that it constitutes a preferably cylindrical hollow space. This hollow space can then be used in the known manner to coat the inner side of the hollow space with a spray device with as less losses as possible. The method according to the invention is preferably to be carried out with a device of the type explained above.
The method can be further developed in such a way that two hollow spaces are formed the one after the other by two opposite curvatures of the flexible side of the carrier frame, the inner side of the hollow spaces being respectively constituted by different upper surfaces of the carrier material mat. In this way, a mat can be coated on both sides without requiring further complicated steps except the bending up of the flexible side of the carrier frame from a positive to a negative curvature.
The method according to the invention is preferably constructed in such a way that the axis of the constituted hollow space is orientated vertically. This has the advantage that the gravitation acting onto the spray mists of the spray device cannot result in non-homogeneities of the coating on the mat, since no place of the mat is preferentially oriented with respect to the gravitation.